Approaching HIV cases
Around 38 million people are living with HIV around the globe and as such chances are good that you will encounter a person at risk for or living with HIV in your future practice. Perhaps you will become an Infectious Diseases specialist and this will be your exciting daily work? But even if you enter the field of Emergency Medicine you will still need to know - is this a simple RSV infection or is this an HIV-associated opportunistic infection? If you intend to become a neurosurgeon - is this a meningioma or could it be toxoplasmosis? So let's get started.
Understanding diagnostic testing for, treatment of, and complications associated with HIV all requires some basic virology. To begin, who should be tested for HIV? The CDC.gov website (linked) has a helpful breakdown: who should be tested? along with some additional helpful fact sheets.
There are several generations of HIV tests available. Older (3rd generation) tests relied on host antibody production to the virus which takes some time (anywhere from 3 - 12 weeks). This is called a "window period" in which a person has been infected by HIV but does not yet have detectable antibody. ELISA tests were performed first due to their high sensitivity and then followed by a confirmatory Western blot that seeks to match protein bands of the HIV virus as outlined below.
Find the gp120 and gp41 proteins in the cartoon below. Newer (4th generation) tests also look for antigen from the viral capsid and shorten the window period down to a couple weeks. Find the capsid p24 core ag in the viral particle. If there is concern for an "acute" (< 3-4 weeks ago) HIV infection a nucleic acid test (HIV RNA test) is the test of choice.
There are exceptions to every rule, however generally ALL those infected with HIV should be treated with anti-retroviral therapy. Given non-adherence with therapy can result in genetic mutations limiting future treatment options, there are circumstances in which therapy may be temporarily held until a person is able to regularly take their medication. As we now are treating all HIV-infected patients, labeling someone as having "AIDS" does not often have clinical relevance and continues to have more stigma attached to it than using the term person with HIV virus infection. AIDS does indicate that the person does or once had a CD4+ T cell count of <200 (or <14%) or has had an "AIDS-defining illness" and these low CD4 cell counts are associated with opportunistic infections. CD4 cells have many important functions as Dr. Stephens outlines below, and thus, the lower they drop, the more risk of host opportunistic infection.
Diagnosing and treating AIDS-defining illnesses and opportunistic infections is challenging. The NIH site: hivinfo.nih.gov has a helpful guideline. Click on the link here or the link to the right, then click "guidelines." Now click on "Adult and Adolescent OI Prevention and Treatment Guidelines." Let's say we are concerned with toxoplasmosis. Click on "Toxo." What are the common clinical manifestations? Scroll down...how can we prevent disease with toxoplasmosis? Some important infections and CD4 count associations include:
There are also guidelines for initial evaluation of a "NEW" HIV patient (including which initial labs they will need and which labs should be used to follow them while on treatment) and for choosing anti-retroviral therapy for an adult or adolescent with HIV on the hivinfo.nih.gov site. Scroll back to the top of the the hivinfo webpage and click "guidelines" again and now select "Adult and Adolescent ARV Guidelines." Updates from the last version of the guidelines are described on the right side. On the left choose "What to start." This will give you a helpful reference of the panel's recommendations regarding initial combination regimens for the antiretroviral-naive patient. Find the Panel's recommended anti-retroviral medications within the viral life cycle below.
Given favorable side effect profile, ease of dosing regimen (one pill, once daily) biktarvy (biktegravir/tenofovir alafenamide/emtricitabine) and Triumeq (dolutegravir/abacavir/lamivudine) are 2 of the most popular combinations in regions with good access to care and medication resources/availability. Access to this relatively new medications is limited in developing areas and they may not be the best choice in situations in which compliance with therapy may be low.
Once the patient is on therapy, we monitor symptoms and side effects, the HIV viral load, chemistries and later the CD4 count. Guidelines for additional lab monitoring and evaluation in new patients as well as for those with opportunistic infections are also on the hivinfo site.
